The present invention generally relates to voltage dividing resistor devices for dividing a voltage, and more particularly to a voltage dividing resistor device having a design such that it is easy to manufacture different types of voltage dividing resistor devices which are capable of obtaining different divided voltages.
Generally, a voltage dividing resistor device is employed in a circuit which produces a divided voltage at a high-voltage output stage of a flyback transformer in a color television receiver, for example. This voltage dividing resistor device divides a high-voltage output from a high-voltage coil of the flyback transformer, or divides an output voltage obtained from an intermediate point of the high-voltage coil, and obtains a focusing voltage V.sub.f and a screen voltage V.sub.s by use of the divided voltage.
However, the focusing voltage V.sub.f of an image receiving tube in the recent color television receiver, is usually set to a voltage which is within a range of 20% to 40% of an anode voltage V.sub.a. The value of the focusing voltage V.sub.f depends on the type (or model) and the manufacturer of the color television receiver. The standard value of the focusing voltage V.sub.f is set within a range of .+-.2% of the design center value, and the focusing voltage V.sub.f is actually variable within a range of approximately +3% of the design center value. But since the focusing voltage V.sub.f greatly differs depending on the type of the color television receiver, even among the color television receivers of the same manufacturer, it is virtually impossible to design a voltage dividing resistor device having a large variable range so that it is possible to obtain the focusing voltage V.sub.f for each of the types of color television receivers. Accordingly, it was necessary to manufacture different types of voltage dividing resistor devices for each of the types and manufacturers of the color television receivers.
In other words, when the receiver, the type of the image receiving tube, the model or the like differ, the optimum focusing voltage V.sub.f and the screen voltage V.sub.s respectively differ. Among the image receiving tubes of the color television receivers which are presently marketed, a ratio V.sub.f /V.sub.a between the focusing voltage V.sub.f and the anode voltage V.sub.a is generally selected to 0.24, 0.28, 0.32, and 0.38. Thus, the resistances. resistors within the voltage dividing resistor device must be selected so that the optimum ratio V.sub.f /V.sub.a can be obtained for the image receiving tube which is to be used. On the other hand, the screen voltage V.sub.s differs depending on the operating condition of the image receiving tube, but it should be able to obtain a voltage in the range of 200 volts to 1000 volts.
However, the voltage which is applied to the voltage dividing resistor device is not constant. Especially in the case of a circuit which obtains an output voltage from an intermediate point of the high-voltage coil of the flyback transformer, the output voltage differs depending on the type of the color television receiver. Hence, a voltage dividing resistor device having a voltage dividing ratio which is dependent on the combination of the image receiving tube and the flyback transformer, had to be designed and prepared for each of the types of color television receivers.
Conventionally, when manufacturing voltage dividing resistor devices having different voltage dividing ratios, electrodes were printed by use of the same electrode pattern because the locations of terminals which are connected to the electrodes and the locations of shafts of the variable resistors are the same for each of the voltage dividing resistor devices having the different voltage dividing ratios unless the design of the device is changed. Thereafter, the resistances were set by suitably setting the ratios between lengths of resistor patterns. The resistor bodies were printed by use of a screen mask for forming the resistor pattern. The screen mask was designed so that a total resistance which is the sum of the resistances of the resistor patterns is the same for each of the voltage dividing resistor devices.
Accordingly, when manufacturing different types of voltage dividing resistor devices having different voltage dividing ratios according to the conventional method, the screen masks for forming the resistor patterns so as to obtain the resistor bodies having different resistances, were prepared for each of the types of the voltage dividing resistor devices. Hence, when manufacturing the different voltage dividing resistor devices, the screen mask for forming the resistor pattern had to be changed for each voltage dividing resistor device. In a case where the screen mask is changed to manufacture the different types of voltage dividing resistor devices, the thickness of emulsion on the screen mask, the mounting state of the screen mask on a printer, the tension in the screen mask, the inclination of the squeeze, the coefficient of viscosity of a resistor paste, or the like differ every time the screen mask is changed Thus, a test print had to be initially made to determine whether a desired characteristic can be obtained by baking the test printed resistor bodies. Due to this necessity to make the test print and perform the checking operation to determine whether the desired characteristic can be obtained by baking the test printed resistor bodies every time the screen mask is changed, the productivity was poor. In other words, as the number of times the screen masks are to be changed increased, it took more time and manpower to perform the checking operations. Therefore, there was a problem in that the manufacturing cost of the voltage dividing resistor device became high.